1. Field of the Invention
The invention relates to a process for suppressing torque jumps during operation of an internal combustion engine, in which a calculated total injection quantity of fuel to be supplied to a cylinder of the internal combustion engine is metered as a function of an operating point of the internal combustion engine, either during a single injection process or by dividing into two injection processes per cylinder stroke, a pilot injection quantity is metered during a first injection process and a main injection quantity is metered during a second injection process.
In a diesel internal combustion engine, in particular in a direct injection diesel internal combustion engine, combustion noise can be considerably reduced if the fuel quantity is not injected once, but is divided into two injections per cylinder stroke. First, a small, so-called pilot quantity, and then, according to a spacing angle, a main quantity, is injected into the cylinder according to German Published, Non-Prosecuted Patent Application DE 39 35 937 A1. That achieves a reduction of a fuel chamber pressure gradient and consequently a slower buildup of pressure in the combustion chamber.
U.S. Pat. No. 4,782,803 has disclosed a process for controlling the fuel injection for a fuel injection pump, with a high pressure chamber that can be connected to fuel injection nozzles of an internal combustion engine. The fuel is subjected to pressure in the high pressure chamber and the pressurized fuel is fed from there to fuel injection nozzles. The pump furthermore has a low pressure chamber, with a connecting path connected to the high pressure chamber and the low pressure chamber, and has a solenoid valve for selectively closing and opening the connecting path, wherein during the pressurization of fuel in the high pressure chamber, the solenoid valve is selectively closed and opened in such a way that a pilot injection and then a main injection are executed and a start time and end time of the pilot injection are defined as a function of working conditions of the machine.
The noise behavior must be improved, primarily at low or average speeds or rpms and up to average loads, while at high speeds and high loads, there is too little time for a pilot injection. Therefore, the pilot injection must be switched on and off depending upon the operating point.
At a transition from the pilot operation into the non-pilot operation and vice versa, torque jumps can occur that reveal themselves as a jerkiness in the vehicle driven by the internal combustion engine and excite vibrations in the vehicle. Therefore, a torque compensation must be established between the types of operation.
Transition functions, which gradually adapt the pilot quantity or the spacing of the injections, cannot be carried out for the following reasons:
The effective pilot quantities are very small and range along the lower limit of the minimally meterable injection quantities. A gradual increase from zero to the desired pilot quantity or a slow return is therefore not possible. PA1 A minimum spacing must exist between the pilot and the main injection time since otherwise the two combustions coincide and the combustion chamber pressure increases considerably.